When your armor causes you to fail at casting a spell, you do not lose the spell or spell slot and can use it again later.
Benefit: When you fail to cast a spell as the result of an arcane spell failure roll, you do not lose the spell or spell slot. You still fail to cast the spell and the action you used to cast it is wasted, but you can attempt to cast the spell again later.
Normal: Normally when you fail to cast a spell as a result of an arcane spell failure roll, you lose the spell.
Undefeatable: The Collected Feats Sourcebook, Copyright 2009 – 2010, Louis Porter Jr. Design, Inc. Undefeated, Copyright 2011, Louis Porter Jr. Design, Inc.